A 26-foot-tall mushroom cloud sculpture, made of giant copper and stainless steel chain-links, has risen among the palm trees on the east side of Main Street, between the courthouse and the Civic Auditorium.

Though the image is of the sky after a nuclear blast, the message is one of peace, according to its creator, Times editorial cartoonist Paul Conrad, working in heavy metal rather than his usual graphite and ink.

"This is a statement of peace," reads the shiny brass plaque at the base of the sculpture, titled "Chain Reaction." "May it never be an epitaph."

But before he could make the piece, Conrad had to fight to gain acceptance for his proposed sculpture, which is his first foray into public art.

The artwork, a 5 1/2-ton creation made of hundreds of feet of gigantic green-tinged chains set in concrete, has raised a lot of eyebrows and a few howls of protest. Some critics say it is more a symbol of war than peace.

"Sure it is," responded Conrad, gazing up at his creation one recent afternoon. "But it's also a peace symbol. The split atom has kept the peace for 40 years."

Other critics had aesthetic differences with the sculpture, which cost about $250,000, donated by an anonymous benefactor.

"I think Paul Conrad is brilliant, but the piece is ugly," said City Councilman Dennis Zane, who voted against putting it in Santa Monica. "That piece in that place is a non sequitur."

Conrad tells of a man-in-the-street critique from a bus driver, who shook his head disparagingly before telling the artist, "I found something dumber than that clown down in Venice."

He was referring to a large mobile sculpture adorning a building at Main Street and Rose Avenue that has an unshaven Emmett Kelly-clown face atop a busty ballerina's body clad in a tutu.

The bus driver notwithstanding, Maria de Herrera, culture and arts administrator for Santa Monica, reports that comment about "Chain Reaction" has been overwhelmingly favorable since its installation earlier last month this month.

"I like the idea of it," said City Councilwoman Judy Abdo. "I like Conrad's sense of humor. He took an image of something very awful and created an art piece that became a reminder to all of us not to ever get involved in a nuclear war."

Abdo was in the majority when the council voted 4 to 3 in 1990 to bring the mushroom cloud to its resting place in the Civic Center. The vote marked the beginning of the end of the lengthy effort to find a home for Conrad's creation.

Conrad had approached Santa Monica more than four years ago with an idea he said had originated from his two-dimensional cartoon drawings of the aftermath of a nuclear reaction. "Wouldn't that look great (as a sculpture)? " he recalled thinking. "Then I decided, 'Let's go big,' " he said.

In keeping with the subject matter, the reaction was explosive. "Chain Reaction" was either wondrous or worthless, depending on whom you asked. After one public hearing, Conrad complained, "I don't think any artist should have to go through this."

The Santa Monica Arts Commission voted four times unanimously to accept the piece. The public, however, confronted with a model of the sculpture in City Hall accompanied by a ballot box to give opinions, voted it down, 730 to 392. The Arts Commission chose to disregard the poll on the grounds that voting wasn't monitored and that people could have stuffed the ballot box.

The message and the medium were far from the only points of contention. Where to put such a dominant artwork also came into play. It was once slated for the front of the gym at Memorial Park, but Conrad says its final resting place is the spot he favored all along.

For a time in 1989, it looked as if "Chain Reaction" might go elsewhere. Frustrated by delays in Santa Monica, Conrad offered the sculpture to Beverly Hills.

Officials there concluded that the city had no place for it--but not before the sculpture and the artist took some additional flak. At the time, a few of Conrad's cartoons depicting the Palestinian struggle against Israeli occupation were evoking anger in segments of Beverly Hills' large Jewish community. Some of the critics accused Conrad of anti-Semitism and mounted a letter-writing campaign to veto the sculpture because of the unrelated cartoons. Conrad categorically denied being anti-Semitic.

Meanwhile in Santa Monica, the peace activists eventually carried the day with the argument that the sculpture expressed a message on which there was a broad consensus in the liberal community: War is hell.